1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method that perform color conversion processing on color image data and outputs monochrome image data.
2. Description of the Related Art
Scanners installed in monochrome multi-function peripherals (MFPs) conventionally have one light source and one type of sensor. When copying monochrome documents using such a configuration, it is possible to maintain the gradation; however, when copying color documents with such a configuration, some colors will disappear, appear patchy, or the like due to the spectral properties of the light source, the sensitivity of the sensor, and so on.
For example, there is a problem that while a red document can be accurately copied in monochrome, copying a yellow document in monochrome results in data loss.
FIG. 1 is a diagram illustrating such a problem, where copying using a monochrome multi-function peripheral results in data loss. 101 is a monochrome document, 102 is a red color document, and 103 is a yellow color document; 104 to 106 represent the results of making monochrome copies of the documents 101 to 103. As shown in FIG. 1, the monochrome document 101 is faithfully reproduced in the result 104. The red color document 102 is also faithfully reproduced in the result 105.
However, the data toward the highlight side of the yellow color document 103 is lost in the result 106. Of course, the colors for which data tends to be lost differ from device to device, and thus the actual result may not necessarily correspond exactly to the result shown in FIG. 1.
As opposed to a monochrome MFP, which has a single type of sensor, scanners installed in conventional color MFPs have three types of sensors for a single light source, and separate scanned data into three types of data, or A, G, and B. When making a monochrome copy, the monochrome data is created by mixing the RGB data at a certain ratio. This has an advantage in that the color separation capabilities are higher than those of the monochrome MFP, which has only a single sensor.
This advantage makes it possible for a color MFP to reproduce colors that would disappear with a monochrome MFP when making a monochrome copy of a color document. However, because three types of sensors are driven, there is a problem that making a monochrome copy takes a similar amount of time as making a color copy.
Accordingly, a technique for improving the speed of making monochrome copies in a color MFP by driving three types of sensors when making a color copy and driving only one of those types of sensors when making a monochrome copy has been proposed (for example, see Japanese Patent Laid-Open No. 2005-252636).
However, because the abovementioned conventional technique uses only a single type of sensor when making a monochrome copy, there is a problem that specific colors cannot be reproduced when copying a color document, as is the case with a monochrome MFP. In addition, as described above, if the document is scanned using the three types of sensors in order to increase the reproduction accuracy, the driving time is longer than when using a single sensor, resulting in a problem that the time a user must wait increases.